Types of medicine
What Is an Alpha-Blocker? Uses and Label Warnings
Alpha-blocker · say it: AL-fuh BLOK-erAlso written: alpha blocker, alpha-adrenergic blocker, alpha-1 blocker
Short answer
An alpha-blocker is a medicine that relaxes certain muscles, used to ease urine flow in an enlarged prostate and sometimes to lower blood pressure.
What it means
Alpha-blockers block alpha receptors, which tighten smooth muscle in blood vessels, the prostate and the bladder neck. Relaxing these muscles makes it easier to pass urine in benign prostatic hyperplasia (BPH), and can also lower blood pressure. Examples include tamsulosin, alfuzosin, doxazosin, terazosin and prazosin. Names usually end in '-osin'.
Their labels warn about dizziness and fainting from low blood pressure on standing, especially after the first dose or a dose increase, so they are often started at bedtime. They also warn about 'floppy iris syndrome' during cataract surgery, so you should tell your eye surgeon you take one. Combining with erectile dysfunction medicines can add to blood pressure lowering. Rarely they can cause priapism.
Alpha-blockers are different from beta-blockers, which mainly slow the heart. They are also different from 5-alpha-reductase inhibitors, which shrink the prostate slowly.
Where you may see it
- 'Warnings' sections of tamsulosin, doxazosin and alfuzosin labels
- Leaflets ('take at bedtime', 'rise slowly')
- Urology letters and pre-operative eye surgery checklists
📄 How it looks on a report
Intraoperative floppy iris syndrome has been observed during cataract surgery in some patients treated with alpha-1 blockers.
🙅 What it does not mean
- It is not the same as a beta-blocker.
- Dizziness at the start does not always continue, but get up slowly and tell your doctor if it persists.
- It eases symptoms but does not shrink the prostate.
🗒️ Questions to ask your doctor
💊 Medicines whose labels mention “Alpha-blocker”
Plain-English explanations of each medicine, from its official FDA label.
- Carvedilol
A beta-blocker. The FDA lists it as both an alpha-adrenergic blocker and a beta-adrenergic blocker.
- Metoprolol Tartrate
A beta blocker. The label describes it as a selective beta-1 adrenergic receptor blocking agent, which means it mainly blocks beta-1 receptors, found largely in the heart.
- Sildenafil
A phosphodiesterase-5 (PDE5) inhibitor, a medicine used to treat erectile dysfunction
- Tamsulosin
An alpha-blocker medicine. The label calls it an alpha 1 adrenoceptor antagonist that acts on the prostate. The FDA class is not listed.
🔗 Read more from trusted sources
- “Alpha-blocker” on MedlinePlus ↗
US National Library of Medicine
- NCI Dictionary definition ↗
US National Cancer Institute: “alpha blocker”
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